Weathering and potassium release from different sized biotite and moscuvite Micas in rhizosphere of canola (Brassica napus)

The objective of this research was to demonstrate the ability of canola to take up structural potassium from muscovite and biotite. The experiment was carried out in a completely randomized design with factorial combinations and three replicates. Culture medium was a mixture of sandy quartz and K-bearing minerals including muscovite or biotite with two sizes: <4 μm and 4-60μm (as silt) and the plants fed during a period of three-months by two different nutrient solutions (K+ and K–). At the end of the experiment, shoots were separated and their K content was determined with flame photometer. In- K treatment, total K uptake of plant was significantly influenced by the type of culture medium. The maximum K absorption was related to plants grown in culture medium containing biotite. However, the minimum value was observed in the muscovite and quartz bearing medium with K-free nutrient solution. Mineralogical results after treatment showed clay size biotite which was fed with K-free nutrient solution weathered more than silt sized biotite and partially transformed to vermiculite because in smaller size, the confinement layers of potassium are more weathered and will release their K more quickly and release it to the plant. On the contrary, there was no significant difference in the degree of muscovite weathering when fed with K+ and K– free nutrient solutions in both media. Muscovite was resistant in this situation.